Condition: YourControl == true (make sure you use the "Named Controls" tab of the formula builder)

Now whenever someone checks the "Disapprove" checkbox, the field where the rule is applied on gets disabled (read only). For doing the same for the "Approve" checkbox, just create another rule for this control and change the named control in your condition.

Condition: YourControl == true (make sure you use the "Named Controls" tab of the formula builder)

Now whenever someone checks the "Disapprove" checkbox, the field where the rule is applied on gets disabled (read only). For doing the same for the "Approve" checkbox, just create another rule for this control and change the named control in your condition.